EDTA (ethylene diamine tetraacetic acid) is used as a chelating agent for cleaning scale from steam generators used for pressurized water reactors. These steam generators accumulate great quantities of precipitated iron oxides that reduce the heat transfer coefficient and the efficiency of the steam generator. Periodically, it is necessary to clean the precipitated material from these steam generators.
A 10-15% ammonium EDTA salt solution is typically injected into the steam generator. Since EDTA is a powerful chelating agent, it coordinates the iron and solubilizes it. In nuclear power plants, the shell side or secondary side of these steam generators is supposed to be the "clean" side. However, minor leaks in the tubes may occur allowing material from the primary side to leak low levels of radioactivity to the "clean" side, primarily in the form of radioisotopes of cesium cobalt and other metals.
Acidifying the metal salt containing EDTA chelating solution produces a metal salt contaminated H.sub.4 EDTA. The cost of stabilization, transportation and disposal of these wastes are high, making volume reduction of the metal salt containing H.sub.4 EDTA precipitate a cost-effective alternative.